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      <title>在分布式系统中实现分布式事务 - 交互式测验</title>
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    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>在分布式系统中实现分布式事务 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
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                    <div id="question-container">
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                    <div id="hint-container" class="hint-container"></div>
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                <div class="quiz-footer" id="quiz-footer">
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      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，两阶段提交（2PC）方案在可用性方面存在一个主要缺陷，这个缺陷是什么？",
    "options": [
      "协调者是单点故障，其宕机可能导致参与者资源被长期锁定。",
      "它无法保证事务的ACID特性。",
      "网络通信开销过大，导致性能无法接受。",
      "实现逻辑比TCC或Saga模式更复杂。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "2PC的一个核心问题是其对协调者的严重依赖。如果协调者在第二阶段（提交/回滚）前宕机，所有参与者将无法确定最终事务状态，导致资源被锁定，从而影响整个系统的可用性。",
    "source": "文档中「二、常见的分布式事务方案 -> 1. 两阶段提交（2PC, Two-Phase Commit）」部分的「缺点」",
    "hint": "思考一下如果负责发号施令的“协调者”突然消失了，等待指令的“参与者”会怎么样？"
  },
  {
    "question": "在TCC（Try-Confirm-Cancel）模式中，'Try'阶段的核心职责是什么？",
    "options": [
      "直接提交业务操作的最终结果。",
      "检查并预留业务资源，为后续的Confirm做准备。",
      "向协调者发送一个准备就绪的信号。",
      "如果其他服务失败，则执行回滚操作。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "'Try'阶段是TCC模式的第一步，其主要任务是检查业务可行性并预留必要的资源。它并不执行真正的业务提交，而是为第二阶段的Confirm或Cancel操作做好准备。",
    "source": "文档中「二、常见的分布式事务方案 -> 3. TCC（Try-Confirm-Cancel）模式」部分的「概念」",
    "hint": "TCC模式的第一步是“尝试”，它需要为后续的“确认”或“取消”做准备。"
  },
  {
    "question": "Saga模式是如何实现分布式事务的回滚和数据一致性的？",
    "options": [
      "通过在事务开始前锁定所有相关资源。",
      "依赖一个中央协调者来执行两阶段提交。",
      "为每一个正向的局部事务设计一个对应的补偿事务，在失败时反向执行。",
      "通过消息队列的重试机制来保证所有操作最终成功。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "Saga模式的核心思想是将长事务分解为多个局部事务。为了处理失败情况，它要求为每个局部事务都提供一个补偿操作。当某个局部事务失败时，系统会依次调用前面已成功事务的补偿操作，从而使系统状态回退到事务开始前的状态，保证最终一致性。",
    "source": "文档中「二、常见的分布式事务方案 -> 5. 基于数据库的事务管理（Saga模式）」部分的「概念」",
    "hint": "当一个长流程中的某一步失败时，Saga需要一种机制来“撤销”已经完成的步骤。"
  },
  {
    "question": "在电商平台的订单创建流程中，涉及“创建订单”、“扣减库存”、“增加积分”等多个微服务。如果系统要求高吞吐量，并能容忍数据在短时间内不一致（例如，积分在订单完成后几秒内到账），哪种分布式事务方案最为合适？",
    "options": [
      "两阶段提交 (2PC)",
      "可靠消息最终一致性",
      "三阶段提交 (3PC)",
      "仅使用本地事务而不做协调"
    ],
    "correctAnswerIndex": 1,
    "explanation": "该场景强调高性能和最终一致性，而非强一致性。可靠消息最终一致性方案通过异步消息解耦服务，避免了同步阻塞和资源锁定，天然适合高并发场景，并通过消息队列的可靠投递和重试机制确保数据最终达成一致。",
    "source": "文档中「二、常见的分布式事务方案 -> 4. 可靠消息最终一致性（基于消息队列的事务方案）」部分的「适用场景」以及「三、分布式事务方案选择的考虑因素」",
    "hint": "思考哪种方案最适合异步、解耦且不要求“立即”一致的场景。"
  },
  {
    "question": "与2PC相比，TCC模式在处理高并发业务时的一个显著优势是什么？",
    "options": [
      "TCC的实现复杂度远低于2PC。",
      "TCC可以保证比2PC更强的ACID特性。",
      "TCC在业务执行阶段不长期锁定资源，从而提高了并发性能。",
      "TCC完全消除了对网络通信的依赖。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "2PC在整个事务期间（从准备阶段到提交阶段）都需要锁定资源，这在高并发下会成为性能瓶颈。而TCC模式通过业务层面的资源预留（Try）代替了数据库锁，锁的粒度和持有时间都大大降低，因此在高并发场景下性能更好。",
    "source": "文档中「二、常见的分布式事务方案 -> 3. TCC（Try-Confirm-Cancel）模式」部分的「优点」",
    "hint": "在高并发场景下，长时间“锁定”资源是性能杀手。哪种方案能更好地避免这个问题？"
  },
  {
    "question": "哪种分布式事务方案特别强调需要为业务逻辑的每个操作都实现正向执行、确认和撤销三个接口？",
    "options": [
      "Saga模式",
      "TCC（Try-Confirm-Cancel）模式",
      "两阶段提交 (2PC)",
      "可靠消息最终一致性"
    ],
    "correctAnswerIndex": 1,
    "explanation": "TCC模式的名称本身就定义了它的三个核心阶段：Try（尝试）、Confirm（确认）和Cancel（取消）。这种模式要求业务代码对每个事务参与方都提供这三个操作的实现，因此具有较强的业务侵入性。",
    "source": "文档中「二、常见的分布式事务方案 -> 3. TCC（Try-Confirm-Cancel）模式」部分的「概念」和「缺点」",
    "hint": "这个问题的答案就在方案的名称里。"
  },
  {
    "question": "在选择分布式事务方案时，如果业务场景（如金融转账）对数据一致性要求极为严格，不允许出现任何中间状态或最终不一致的情况，应优先考虑哪类方案？",
    "options": [
      "Saga模式或可靠消息最终一致性",
      "两阶段提交 (2PC) 或三阶段提交 (3PC)",
      "仅使用TCC模式",
      "不使用任何分布式事务，依赖手动校对"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，2PC和3PC能够保证严格的ACID特性，提供强一致性保障。虽然它们在性能和可用性上有所欠缺，但在金融等对一致性要求苛刻的场景中，这种保障是首要的。而Saga、TCC和消息队列方案通常用于实现最终一致性。",
    "source": "文档中「三、分布式事务方案选择的考虑因素」部分的「1. 一致性需求」",
    "hint": "在“一致性需求”这一节中，文档将方案分为了“强一致性”和“最终一致性”两类。"
  },
  {
    "question": "三阶段提交（3PC）相比于两阶段提交（2PC）做出了一项关键改进，这项改进是什么？",
    "options": [
      "它完全移除了协调者角色。",
      "通过增加一个“预提交”阶段，减少了协调者宕机时参与者的阻塞时间。",
      "它采用了消息队列来异步通信，提高了性能。",
      "它将事务的ACID保证级别从强一致性降为了最终一致性。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "3PC是对2PC的优化，其核心改进是引入了“预提交”阶段。这个阶段在准备阶段和正式提交阶段之间，旨在减少因协调者故障而导致的参与者长时间阻塞和数据不一致的风险。",
    "source": "文档中「二、常见的分布式事务方案 -> 2. 三阶段提交（3PC, Three-Phase Commit）」部分的「概念」",
    "hint": "3PC比2PC多了一个阶段，这个阶段起到了什么作用？"
  }
];
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            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  